1. Field of the Invention
The invention generally relates to redundant motor drive systems and more particularly to a redundant motor drive system characterized by two motors and separate gear trains, each being adapted to perform a driving function without backdriving the other.
2. Description of the Prior Art
The most pertinent prior art references noted during a preliminary search for the invention herein described and claimed are as follows:
______________________________________ 3,214,999 Lapp Nov. 2, 1965 3,628,862 Stephenson Dec. 21, 1971 3,768,325 Kucharski, Jr. Oct. 30, 1973 3,866,486 Lechner Feb. 18, 1975 3,986,412 Farley Oct. 19, 1976 ______________________________________
It is noted that U.S. Pat. No. 3,214,999 discloses a dual-stage drive comprising two motors which may be driven at different speeds to provide variable speeds or directions of rotation. However, this patent does not disclose a redundant drive means as disclosed and claimed in the instant application.
U.S. Pat. No. 3,628,862 is believed to be pertinent because it discloses two separate electric motors and two separate worm gear drives, with the worm gear on the output shaft of each motor being disposed in driving engagement with a sector worm. Selected energization of one or the other of the motors is arranged to angularly position a motor or reflector to a limited extent of the worm gear sector. However, this arrangement of drive means is not considered to constitute a redundant drive motor arrangement, as herein disclosed and claimed, but rather comprises a system which provides two motors for achieving different directions of rotation.
U.S. Pat. Nos. 3,768,325 and 3,866,486 are believed to be of general interest in that they show worm gear drives which block backdrive. Again, there is no disclosure of a system through which redundant operation is accommodated through multiple sets of independent motors and gear trains as is provided for through the instant invention.
U.S. Pat. No. 3,986,412 relates to a dual motor redundant drive system which employs separate planetary gear reducers and bearings differing structually and functionally from the invention as hereinafter disclosed and claimed.
It will, of course, be appreciated that in many instances it is highly desirable to provide for redundancy, whereby back-up is always available. Such instances are frequently found in the aerospace industry wherein failure of a motor or system can severely jeopardize an otherwise successful mission. Of course, where multiple motors are employed for driving a common rotary output shaft it often is necessary to provide means for selectively coupling the motors with the shaft through a use of clutches and the like. This leads to complexity in design. Alternatively, backdriving one or more of the redundant motors has been resorted to, but such technique increases power requirements. In either instance, it can be seen that problems relating to excessive costs and complexity continue to plague designers of systems requiring a high degree of reliability.
It is therefore the general purpose of the instant invention to provide an improved and simplified redundant motor drive system which includes a plurality of motors, each being continuously interconnected and adapted to drive an output shaft without backdriving the other motor.